Against a background of increasing miniaturization of electric devices, an increasing number of chip resistors are used in recent years. In addition, along with the growing demand of mounting electric devices by a surface mounting, carbon-film resistors with lead wires are actively replaced with chip resistors. Consequently, demands for new properties such as surge property have been increasing to chip resistors. In general, the resistance of a resistor can easily fluctuate when a surge voltage generated by static electricity or noise in the power source is applied. However, it is known that the longer and wider the resistor element, the less the resistance value fluctuates.
One of the well-known prior arts has been disclosed in the Japanese Patent Laid-open Publication No. H01-42102 (S64-42102). To reduce the noise of the resistor element, any number of slits are provided alternately from the two facing sides of the rectangular resistor element so that the current path in the resistor element becomes longer by a zigzag pattern.
The chip resistor disclosed in the Japanese Patent Laid-open Publication No. H09-205004 comprises a resistor element which is formed between a pair of electrodes by a printing or trimming method, or by both methods in combination, in a manner that the resistor element are bent three times or more between the two electrodes.
As shown in FIG. 2, however, in the case of the chip resistor disclosed in the Japanese Patent Laid-open Publication No. H01-42102 (S64-42102), when a slit 4 is not provided, a resistor element 3 becomes shorter. On the other hand, when a plurality of slits 4 are provided, the resistor element 3 becomes thinner, and is changed in resistive property by heat applied during the laser trimming processes, lowering its surge property. Conventionally, during the laser trimming, the resistor element 3, along with a substrate 1, is cut to form a groove that reaches under a surface of the substrate and has a bottom lower than the surface. Formation of five slits 4 by laser increases man-hours, thus productivity decrease.
As shown in FIG. 3, with the prior art disclosed in the Japanese Patent Laid-open Publication No. H09-205004, the chip resistor can not be downsized with the printing method. In other words, when considering a required width of the resistor element and space between neighboring pattern, a resistor of size 2012 (2.0 mm×1.25 mm) for example, can only be bent once or twice. In FIG. 4, by the combination method of printing and trimming, a resistor element 8 with two turns is printed between electrodes 6 which are disposed on both ends of a substrate 5. In this case, due to alignment failure of printing, and smearing or sagging of the resistor element 8, spaces between the electrodes 6 and the resistor element 8 is filled, thus a desirable length of the resistor element can not be obtained. Furthermore, since there is no other trimmed section besides a trimming groove 9, ratio of the resistance adjustment is limited and production yield is low. The present invention aims to address the foregoing problems and to provide a compact resistor having a superior surge property.